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COMMENTARY |
Division of Geriatric Medicine, Saint Louis University School of Medicine, St. Louis, Missouri.
Address correspondence to Margaret-Mary G. Wilson, MD, Division of Geriatric Medicine, Saint Louis University School of Medicine, 1402 S. Grand Blvd., M238, St. Louis, MO 63104. E-mail: wilsonmg{at}slu.edu
I do not believe in ... immortality; it seems so unnecessary.—Edward Abbey, Pennsylvania Poet (1927–1989)
Fundamental principles of geriatrics are by no means novel. Indeed, they stem from a singular core theory that holds true for both animate and inanimate objects. Succinctly summarized, this theory is best stated as the fact that improved care enhances longevity. Surprisingly, for decades, this basic tenet has been relatively ignored as seemingly more advanced science introduced paradoxically retrogressive hypotheses that undercut the role of natural selection pressures in influencing the life expectancy of all species (1). Disease and a multitude of other extrinsic mishaps, on both individual and population levels, were blamed, almost exclusively, for the premature demise of humans. Eventually, logical appraisal of available evidence mandated the realization that eliminating all pathogenic and violent causes of death would only serve to delay or prolong the process of dying. Perhaps in an attempt to account for this observation, scientists then sought multiple alternative population aging theories that they hoped could be adapted to explain cohort-specific differences in longevity.
Thankfully, Robine and Michel take us back to the drawing board and acknowledge the shortsightedness of previous conceptual models of population aging (2). The authors discuss several well-known theories of population age structure, namely demographic transition, epidemiological transition, and rectangularization of the curve (3–5). Notably, stability is one of the foremost attributes of the rectilinear age structure that characterizes the latter theory.
More children surviving to adulthood will eventually negate transient widening of the base caused by decreased infant mortality rates. Similarly, transient narrowing of the base of the population age structure, resulting from subsequent reduction in birth rates, will eventually be offset as older adults die, resulting in a return to a rectangular age structure. Thus, it may be argued that stability of the rectilinear population structure depends on survival, not of the older segment, but of the young and middle aged. Robine and Michel also refer to Fries' "compression of morbidity" theory. Although favored by some, it may be argued that Fries' theory is not only shortsighted but indeed merely a paradigm based on unfounded projections that subtly, and unrealistically, presume absolute foreknowledge of the human life span; thereby allowing only finite room within the curve for expression of morbidity (6).
Strikingly, a central theme shared by all these models is the flawed hypothesis that the key to longevity lies mainly in the pursuit and conquest of diseases. With this in mind, it is of concern that the authors attempt to justify the need for a new theory of population aging by invoking the differences observed in levels of frailty among diverse populations. The authors expend considerable effort in highlighting the difference in age structure, functional disability trends, and limitations between different countries. However, it is worthwhile to point out that any objective attempt to discuss the data exclusively from a medical standpoint is tantamount to "... ignoring the elephant in the room." Estes and others theorize correctly that "... reducing problems of aging to the individual level shifts any onus of responsibility from the state to the individual ... [thus] inequities in resource distribution and access can be ignored" (7). Perhaps this is a reflection of society's subconscious attempt to relinquish any social or moral responsibility toward the aging segment of the population (8). Surely, any plausible unifying theory that seeks to marry longevity, functional disability, and health perception must involve political, social, cultural, psychological, and economic factors. Furthermore, the functionality of any such theory will be tested by the degree to which each society interjects ageism into the definition of public policy.
Granted the population age structure is more rectangular in developed countries such as Switzerland, Sweden, and Japan (9,10); however, with technological, medical, and socioeconomic advances, rectilinear population structures will become increasingly more common. In an attempt to strengthen the case for a new theory of population aging, the authors correctly ascribe progressive rectangularization of the curve to a fall in the mortality rate among older adults in low-mortality countries. However, the authors then circuitously attempt to link reduced death rate in older adults, not only with increased life expectancy, but also with increased life span. While the former association is well established, the latter is mere conjecture. Nevertheless, it is in discussing the disability transition that one could argue that the authors begin a slippery descent (2). Clearly, any life-threatening illness for which only suppressive treatment is available will result in the emergence of a chronic illness. Thus, in such circumstances, death from disease is exchanged for disability of varying degrees. Subsequently, as society, medicine, and technology provide more advanced and effective treatment options, it is quite reasonable to expect that the affected individual's perception of the severity of the disease burden will drop. Thus, the disability transition is far from an epidemiological mystery, and is in fact a logically sound socioeconomic phenomenon. Quite rightly, the authors make only brief reference to Olshansky's theory of the "Age of Degenerative Diseases," which at best can only be described as a redundant and tautological description of well-recognized implications of aging and senescence in any species (11).
Although, eventual "compression of morbidity" may be inferred from available American data, this observation may be premature for a number of reasons. Foremost among these is the ongoing metamorphosis of the spectrum of age-related morbidity. Previously accepted "normal" age-related occurrences, such as muscle loss and reduced libido in men, are now categorized as diseases, namely sarcopenia and andropause (12). Ironically, the resultant morbidity expansion occurring from such redefined syndromes shifts the area under the morbidity curve in the direction of middle age, thereby introducing the concept of age-related morbidity at an earlier stage in life. On the other hand, with increasing utilization of palliative care, dying has become a more efficient process, thereby contributing to limitation of the morbidity curve from the terminal end of the age spectrum (13). From a third perspective, a strong opposing argument can even be made for the complete nonexistence of dynamic intrinsic morbidity. Proponents of the latter viewpoint could effectively advance the alternative theory of an expansion of environmental age-friendly modifications, increased social awareness, heightened political consciousness, and more sophisticated public policy within a cohort of better-educated adults. Such socioeconomic advances would conceivably limit the perceived burden of morbidity, thus creating merely the appearance of morbidity compression. However, implicit in the enthusiasm underling the ongoing controversy is the false assumption that the interaction of comorbidity and outcomes such as frailty can be objectively measured in units that will allow accurate comparisons within and between diverse cohorts. Available evidence shows that patient perception of health status is a more reliable predictor of health outcomes than objective parameters (14). Thus, objective comparison will always be confounded by differences in subjective perception of well-being and sociocultural mores, as well as variations in each society's level of economic, medical, and technological sophistication.
Perhaps the boldest and most controversial claim made by the authors is that their framework for a general theory of population aging may also explain the emergence of frailty. The authors maintain that frailty is exclusive to the "highest ages," and imply that the consequences of frailty are responsible for current mortality plateaus (2). These unidimensional and most likely erroneous attributes of frailty, favored by biomedical demographic researchers, unjustifiably equate frailty with disability and increased risk of death. More comprehensive models view frailty, perhaps more accurately, as a multidimensional dynamic construct arising from a complex interplay of physical, environmental, sociocultural, and medical factors, within a relationship matrix interwoven from the fabric of the individual, family, and relevant caregivers (15). Granted, frailty is more likely to affect older adults. However, as holds true for most geriatric syndromes, age is not the sole determinant of the occurrence or progression of frailty. Furthermore, although the syndrome of frailty is a medically "trendy" diagnosis, it is yet to be accurately defined or characterized. Similarly, cross-cultural comparisons of frailty can only be supported by the unfounded presumption of homogeneity in the presentation of frailty in the older adult. Ultimately, frailty will most likely emerge as a multidimensional syndrome with a multifactorial etiology. Indeed, in light of the current evidence, a diametrically opposing argument can be made that frailty may in fact explain the emerging population age structure and not vice versa.
Cynics may argue that the struggle to redefine aging exists in us all, with normative reference for "old" being oneself. This phenomenon may have spearheaded a global effort, supported by scientists and nonscientists alike, to strive toward immortality. Anti-aging medicine is now frequently confused with geriatric medicine, just as the pursuit of longevity is often misleadingly equated with geriatric health maintenance. The authors logically postulate that increasing life expectancy may result in expansion of morbidity, prior to eventual death. Indeed, such expansion of morbidity could simply be the result of disease arising from genetic and natural selection processes intrinsic to all species. Additionally, the concept of frailty as an embodiment of reduced functional reserves is an inevitable precedent of nonaccidental death at any age (16). Thus, seeking an explanation for the increased incidence of frailty from any general theory of population aging, as the authors suggest, would be redundant.
Robine and Michel's scientific enthusiasm and optimism are admirable and highly commendable. However, the practical challenge facing most geriatricians in the 21st century will not be the development of yet another general theory on population aging. On the contrary, we will be faced with reinforcing the primary goal of geriatric medicine as successful aging, not achieving immortality. Geriatricians cannot do both. Our ultimate challenge is preparing for the self-fulfilling prophecy of good geriatric medicine, which, as the authors' eloquently state, will lead to "... an emergence of the very old and frail populations [and] a new expansion of morbidity" (2).
In their proposed theory, the authors introduce four elements, the most novel of which is an improvement of the health status and health behaviors of the "new cohorts" of old people. It is unclear how the authors suggest that improvement in health status should be measured in a cohort of aging adults in which there is relatively little prior health information. Not surprisingly, this is the only element that attempts, rather unsuccessfully, to explain compression of morbidity.
The authors also propose two avenues to facilitate formulation of a definitive theory of aging: 1) establishing universal indices to measure functional decline, and 2) setting up a multinational body to monitor "global aging" (2). These are probably worthwhile ventures from the epidemiologist's perspective. However, geriatricians will need to weigh ethical considerations against such scientific observation. Studying global aging from the scientific perspective will be unavoidably confounded by the quality of local health resources, economic considerations, and sociocultural values. Ethically and logistically, all of these factors defy randomized and controlled intervention. The alternative approach, which is by no means morally acceptable for the skilled geriatrician, is observing the "natural history of aging." Thus, I disagree with the authors: Monitoring global aging is certainly not an "enthralling challenge" for the gerontological community.
Sadly, in modern times, the role of devil's advocate has been reduced to voluntary defense of the opposing side of an argument, often merely as a futile intellectual exercise. However, the position of devil's advocate (Advocatus Diaboli) was originally established within Catholicism in 1587 by Pope Sixtus V. The purpose of the appointed officer was to present in writing, for detailed consideration, all possible arguments that could be tendered against the appointment of any candidate nominated for canonization (17). As the Catholic Church would be scandalized by the beatification or canonization of anyone whose life and death could not be juridically proved deserving, the devil's advocate held a critical position in the legal and administrative arms of the Catholic Church. Interestingly, the official title of the devil's advocate was "Promoter of the Faith" (Promotor Fidei), lending further credence to the pivotal role of the appointed officer in Catholic Jurisdiction. Thus, paradoxically, involvement of the devil's advocate was a marker of objective and thoughtful decision making. Within the realm of population aging, the scientific devil's advocate would favor theories of population growth, such as compression of morbidity, because such theories presume progress only when the balance is tilted in favor of survival of only the fittest old. Furthermore, an effective devil's advocate would advance the cause of anti-aging medicine as the only solution. Thus, though one may hold a differing opinion, critical and objective thinkers such as Robine and Michel are to be highly commended for attempting to preemptively thwart such schools of thought. Indeed in conjunction with the rest of the scientific world, the authors share the onus of crafting an effective and convincing population aging theory that soothes the troublesome discourse of "demographic alarmism" (18). Misrepresentation of population aging as an impending social crisis should be firmly discouraged, as this strategy frequently scapegoats dependent and vulnerable older adults (19). Only the extremely naïve gerontologist would pursue "eternal life" at the expense of developing effective strategies to deal with the anticipated issues and concerns of aging. Lest we forget, literary writings speak volumes about the inevitable discomfort associated with entry into the latter stages of life. Isaac Asimov, a science fiction novelist, aptly describes this unwelcome sentiment in his writings, "... life is pleasant, death is peaceful, it's the transition that troubles" (20). Geriatrics is about the transition.
References
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